Let $a, b$, and $c$ be the roots of the cubic polynomial $2x^3 - 3x^2 + 165x - 4$. Compute \[(a+b-1)^3 + (b+c-1)^3 + (c+a-1)^3.\]
Solution: By Vieta's formulas, $a+b+c=\tfrac{3}{2},$ so $a+b-1 = \left(\tfrac{3}{2}-c\right)-1=\tfrac{1}{2}-c.$ Writing similar equations for the other two terms, we get \[(a+b-1)^3 + (b+c-1)^3 + (c+a-1)^3 = \left(\tfrac{1}{2}-a\right)^3 +\left(\tfrac{1}{2}-b\right)^3 +\left(\tfrac{1}{2}-c\right)^3.\]Now, note that $\left(\tfrac{1}{2}-a\right) +\left(\tfrac{1}{2}-b\right) +\left(\tfrac{1}{2}-c\right) = \tfrac{3}{2} - (a+b+c) = 0.$ It's a general fact that if $r+s+t=0,$ then $r^3+s^3+t^3=3rst$; this follows from the factorization identity \[r^3 + s^3 + t^3 = 3 rst + (r+s+t)(r^2+s^2+t^2-rs-st-rt).\]Therefore, \[ \left(\tfrac{1}{2}-a\right)^3 +\left(\tfrac{1}{2}-b\right)^3 +\left(\tfrac{1}{2}-c\right)^3 = 3\left(\tfrac{1}{2}-a\right)\left(\tfrac{1}{2}-b\right)\left(\tfrac{1}{2}-c\right).\]Finally, letting $p(x) = 2x^3 - 3x^2 + 165x - 4,$ we have $p(x) = 2(x-a)(x-b)(x-c),$ so \[78 = p(\tfrac{1}{2}) = 2\left(\tfrac{1}{2}-a\right)\left(\tfrac{1}{2}-b\right)\left(\tfrac{1}{2}-c\right).\]Therefore the answer is \[3\left(\tfrac{1}{2}-a\right)\left(\tfrac{1}{2}-b\right)\left(\tfrac{1}{2}-c\right) = \tfrac{3}{2} \cdot 78 = \boxed{117}.\]